Watercare officials say its 34 per cent rise in legal costs from 2011 to last year came from big construction projects.

Watercare Services is teaching its big brother Auckland Council a lesson in accountability and transparency by releasing details of how much it is spending with city law firms.

Auckland Council is refusing to release details of millions of dollars of spending with city law firms, saying it may prejudice future negotiations.

The only information the council's general counsel, Wendy Brandon, is prepared to release is that the council uses a number of law firms and the five highest paid over the past two years were Brookfields, Buddle Findlay, Kensington Swan, Meredith Connell and Simpson Grierson - in alphabetical order.

Ms Brandon's insistence to limit the details of legal costs from ratepayers is not shared by Watercare's corporate affairs manager, David Hawkins, who has given a breakdown of 33 law firms used by the council body in the past two years and how much each was paid from total spending of $6.26 million.

The figures ranged from $522 to Rob Webber and Associates to $2,686,705 to Russell McVeagh.

The approaches are outlined in information collected by councillor Cameron Brewer into legal costs by the council and seven council-controlled organisations (CCOs).

The figures show that legal costs for Watercare and Auckland Transport increased by 34 per cent and 127 per cent respectively between 2011 and 2012, which both CCOs put down to costs for big construction projects.

Council acting chief executive and chief finance officer Andrew McKenzie said that overall the Auckland Council group had cut its legal costs by about $3.6 million, or just over 9 per cent.

Mr Brewer said Watercare's 34 per cent rise in outside legal costs did not make good reading, but at least they did not hide behind the Local Government Official Information and Meetings Act. "Watercare didn't see the need to protect themselves or the legal firms they use, so I can't see why the rest of the council can't show the same transparency."

Ms Brandon used the act to limit the amount of information released about the council's legal costs, telling Mr Brewer she was confident the council was providing a very cost-effective service to the council and ratepayers.

The Auckland Council has not always been forthcoming about its spending with consultants.

The Ombudsman is investigating a complaint brought by the Herald over a refusal last year by council chief executive Doug McKay to say how much the council paid to consultants - planner Brooke Dales and architect Garry Glasgow - for work on controversial heritage cases at 18 Paget St, Freemans Bay and 38 Hackett St, St Marys Bay.

Figures leaked to the Herald show a council planning unit paid Mr Dales' consultancy firm DCS $95,488 between July 2011 and January 2012.